Recently, discussions for enabling a primarily used frequency band (spectrum) to be used in a second communication service according to the use condition of the frequency band have been in progress. For example, a standard specification for allowing an unused channel (TV white space) included in the frequency band of US digital TV broadcasting to be available for radio communication is under examination in IEEE802.22 working group (see Non-Patent Literature 1 below).
According to a recommendation of the Federal Communications Commission (FCC) on November 2008, the discussions have been directed toward permitting secondary usage of the TV white space by using a communication device that fulfills a predetermined condition and has received an authentication. This recommendation of FCC accepts the standard specification of IEEE802.22, which is the first standardization of secondary usage of the TV white space, and also covers the activities of a new study group in IEEE. Technically, since it is necessary to perform signal detection at a level of −114 [dBm] (SNR is about −19 [dB] when Noise Figure (NF) is 11 [dB], for example) using existing technology for example, an auxiliary function such as Geo-Location Database Access is expected to be necessary (see Non-Patent Literature 2 below). Also, FCC is under examination for opening a 250-MHz band, which is a part of a 5-GHz band, as a new channel for secondary usage.
Furthermore, in the EU, there are moves afoot to universally allocate a dedicated control channel referred to as Cognitive Pilot Channel (CPC) for implementing Dynamic Spectrum Access (DSA) under a long-term strategy. Allocation of CPC has been incorporated in the agenda of International Telecommunication Union (ITU)-WP11 in 2011. Technological studies for a secondary usage system that performs DSA are also under way in the IEEE Standards Coordinating Committee (SCC)41.
In general, when a frequency band assigned to a communication service related to primary usage (will be referred to as a first communication service below) is secondarily used, it is important that a communication service related to secondary usage (will be referred to as a second communication service below) not interfere with the first communication service. For this reason, Non-Patent Literature 2 below recommends installation of a data server that receives administrator information, location information, and the like from a secondary usage node which will provide a second communication service and accumulates these pieces of information in a database. In this case, the data server specifies a channel that can be provided for secondary usage according to a request from the secondary usage node, and notifies the secondary usage node of the specified channel. When the secondary usage node uses the channel notified in this way by the data server, interference with a first communication service is prevented.